The major objective of the Midwinter Conference of Immunologists is to provide an annual scientific meeting conducive to interaction among established senior scientists with new investigators, postdoctoral and graduate students. The goal of the conference is to communicate the most recent developments in the field of immunology. The Midwinter Conference of Immunologists has a long track record of organizing successful meetings. Immune System Development and Function is the topic of the 40th Midwinter Conference of Immunologists in January 2001. Important developments in understanding apoptosis in the immune system will be presented including the role of signal transduction in lymphocyte survival. The number of second signals involved in co-stimulation will be approached in another session. Immune recognition and signaling will encompass the latest data on TCR signaling and genes involved in hematopoietic cell development. Since non- classical MHC molecules play an essential role in immune responses, the structure and recognition of nonclassical MHC will be explored. New insights into factors that determine the fate of a lymphocyte promise to reveal how development of the immune system is regulated at a molecular level. The speakers selected for the 40th Midwinter Conference represent well-known scientists and upcoming young investigators. The program will allow ample time for discussion, exchange of ideas and establishment of collaborations. The 2001 conference promises to be as successful as previous Midwinter Conferences to promote novel ways to explore the immune system.